Model View referring to null reference

Question

I have a view page with multiple models and i am having trouble getting the data to display but i could save any added data just fine. It is just displaying the data on page load tells me that the model i am passing in passes a null reference.

Main view:

@model Project.Models.ProfileModel
@{
    ViewBag.Title = "Profile";
}

<hgroup class="title">
    <h1>@ViewBag.Title.</h1>
</hgroup>


<div id="wrap">
    <div id ="right">
        @(ViewBag.HasLocalPassword ? Html.Partial("_ChangePasswordPartial", Model.PasswordModel) : Html.Partial("_SetPasswordPartial", Model.PasswordModel))

    </div>
    <div id="left">
            @Html.Partial("_UsernamePartial", Model.UsernameModel)
            @Html.Partial("_PlayNamePartial", Model.PlayNameModel)

    </div>

</div>

My models:

 public class ProfileModel
{
    public PasswordModel PasswordModel { get; set; }
    public PlayNameModel PlayNameModel { get; set; }
    public UsernameModel UsernameModel { get; set; }
}

Controller - For each model i have a get and post method except the PlayName just has a GET.

UserName Controller:

public ActionResult _UsernamePartial()
    {
        var usernameModel = new UsernameModel();
        using (var db = new DataContext())
        {
            usernameModel.Username =
                (from u in db.Users where u.ID == WebSecurity.CurrentUserId select u.Username).FirstOrDefault();
        }
        return PartialView(usernameModel);
    }

@Html.Partial("_UsernamePartial", Model.UsernameModel) shows Object reference not set to an instance of an object. and i am not sure how to properly fix this.

public ActionResult Profile(ManageMessageId? message)
    {
        ViewBag.StatusMessage =
            message == ManageMessageId.ChangePasswordSuccess ? "Your password has been changed."
            : message == ManageMessageId.SetPasswordSuccess ? "Your password has been set."
            : message == ManageMessageId.RemoveLoginSuccess ? "The external login was removed."
            : "";
        ViewBag.HasLocalPassword = OAuthWebSecurity.HasLocalAccount(WebSecurity.GetUserId(User.Identity.Name));
        ViewBag.ReturnUrl = Url.Action("Profile");
        return View();
    }

Post for Username:

[HttpPost]
    public ActionResult _UsernamePartial(UsernameModel usernameModel)
    {
        if (ModelState.IsValid)
        {
            using (var db = new DataContext())
            {
                User user = db.Users.FirstOrDefault(u => u.ID == WebSecurity.CurrentUserId);
                user.Username = usernameModel.Username;
                db.SaveChanges();
            }
        }
        return View("_UsernamePartial");
    }

Username Page:

@model Acatar.Models.UsernameModel

@using (Html.BeginForm("_UsernamePartial", "Account")) {

       <p id="legend">Username</p>
       @Html.TextBoxFor(m=>m.Username)

    <button type="submit" value=" Username">Save</button>
}

Answer 1

Your Null Ref was the result of View() Factory call without the bound model.

Answer 2

Use this code in Class

public virtual PasswordModel PasswordModel1 
        {
            get {

                PasswordModel PasswordModel2 = this.PasswordModel.FirstOrDefault();

                if (PasswordModel2 == null)
                {
                    PasswordModel2 = new PasswordModel();

                }

                return PasswordModel2;
            }
        }

use this code in view

@Html.Partial("_UsernamePartial", Model.UsernameModel, new ViewDataDictionary(Html.ViewDataContainer.ViewData)
 {
     TemplateInfo = new System.Web.Mvc.TemplateInfo { }
 })  

Do this For Other Model as well Hope It will help u.